In order to restrain harmonic and improve the quality of the output voltage waveform, an new optimum switching angles modulation method based on in-depth analysis and research on the inverter is proposed in this paper. In this method only the starting point of the modulation pulse waves are optimized, and the width of pulse waves still change as the sine law. The model of filter is taken into consideration while the mathematical model of optimization is set up, in order to minimize the THD of output voltage waveform. At the same time, the sensitivity between the system and the switching angles is considered based on the non-ideal actual situation. The optimal solution of nonlinear transcendental equation is solved under several constraint conditions, and the optimization effects are compared with general SPWM modulation method under different switching frequency, modulation and load resistance. Finally, the reliability of the proposed method is validated through the simulations and experiments.